php8 breaks version 4.2.7

plugin breaks under php 8 with this error.

PHP Fatal error:  Uncaught TypeError: implode(): Argument #2 ($array) must be of type ?array, string given in /www/sbstateofbelief_947/public/wp-content/plugins/addthis-follow/backend/AddThisFollowButtonsToolParent.php:140

this can be fixed by modifying that line to this

$serviceInfo['service'] = implode('_', $parts);